1. Field of the Invention
This invention relates to the preparation of cured polyepoxide coatings using 1,3,5-tris-(2-carboxyethyl) isocyanurate as a crosslinking agent.
2. Description of the Related Art
Coatings prepared by curing polyepoxides with polybasic acid compounds have been described in European Patent No. 480,120; U.S. Pat. Nos. 4,346,144; 4,764,430; 4,681,811; 4,650,718; 4,703,101; 3,787,521; 3,781,380; 3,752,870; 3,730,930; and 4,181,642, and Japanese Patent Nos. 59-107,742; 61-087,767; 61-087,768; and 61-087,769. Reaction of polyepoxides with polybasic acids are further disclosed in the following references: Khim. Tekhnol., No. 3, pages 36 to 39 (1976); Sin. Fiz.-Khim. Polim., Volume 13, pages 41 to 43 (1974); and Pol. J. Chem. Volume 52, Number 7-8, pages 1487 to 1494 (1978).
Coatings prepared by the above-mentioned methods have, in some cases, advantages such as distinctness of image, adhesion and gloss, as disclosed, for example, in the U.S. patents cited above. These coatings, however, suffer from poor solvent resistance and also from poor appearance which is the result of bubbles in the surface of the coating. While introduction of a long chain monocarboxylic acid into the coating may reduce the amount of bubbles popping in the surface of the coating, it also reduces the crosslink density of the coating, thereby reducing the resistance properties of the cured films.
Similarly, for example, even though coatings disclosed in European Patent No. 480,120 have the desirable property of scratch resistance, they also have undesirable properties such as poor gloss. They also require high temperatures to cure.
It is an object of this invention to provide a low temperature curing composition which produces coatings having exceptional solvent resistance and hardness, and, at the same time, having a good balance of other film and resistance properties such as high gloss, and good humidity and salt spray resistance. Hard coatings are particularly useful as chip-, scratch- and mar- resistant automotive coatings and also as general use industrial coatings.